Tighter Quench = Horsepower Loss NA?

[GARY C]

I always wondered if a directed quench would be better then a flat quench but never tested it.

Please tell us you're not referring to Somender grooves! https://www.speed-talk.com/forum/viewtopic.php?t=4069

(The Toyota 1.8 L. in my Vibe has angled squish, aimed up into the middle of the chamber rather than across a flat crown.)

No but I wonder if that is why some have seen improvements, the thing that made me think about it was dropping a 4x8 sheet of plywood on the floor of my shop and watching the dust blow out across the shop.

[GARY C]

I always wondered if a directed quench would be better then a flat quench but never tested it.

Toyota published a paper on the design development of the Toyota 1ZZ-FE engine including a review of flat verses angle quench areas. Angled wins. I have the pdf but not a link. If you haven't seen it pm me an email address.

Whoops... It is a SAE paper (981087)

I have seen several different designs, I thought it would be interesting to test angled toward the Intake side verses the exhaust side vs toward the spark plug.

[Stan Weiss]

I always wondered if a directed quench would be better then a flat quench but never tested it.

Toyota published a paper on the design development of the Toyota 1ZZ-FE engine including a review of flat verses angle quench areas. Angled wins. I have the pdf but not a link. If you haven't seen it pm me an email address.

Whoops... It is a SAE paper (981087)

I have had it for about 10 years. Did a Google search on what mine is called and found this link.
https://www.spyderchat.com/1zzfe.pdf

Stan

[groberts101]

Not sure which engines, but I've read several reports of lost power on some 4 valve stuff where when dual quench pads on both sides of the chambers were modified in a manner that affected mixture motion dynamics.

One scenario involved milling which greatly increased the size of the quench pad on one side of chamber and the other was just the opposite where, iirc the pad was nearly completely removed when larger valves were fitted.

Either way, on a fairly well developed and sorted combo, changing the chambers mixture movement dynamics can easily fudge up the expected results and require counter-measures to regain that lost power.

[vannik]

Stan and David has it right, but some more explanations:

There are two functions:
1. Cooling end gasses to stop detonation, from there the name Quench
2. Enhancing the turbulent intensity to speed up combustion by squeezing out the mixture, from there the name Squish

It is clear that the two are part of the same but not exactly the same. Some general guidelines (sometimes conflicting):
1. Smaller clearance generally speeds up combustion by increasing turbulent intensity, if the combustion process was optimized, this can lead to a power loss.
2. A 1 degree taper usually leads to better results as a parallel clearance can lead to trapped end gas with piston rocking, leading to trapped end gas and more pre-ignition / detonation.
3. Directing the squished flow to the spark plug tip often leads to improvements but sometimes screws up the bulk flow in the chamber which leads to worse power.
4. Sometimes adding more waterflow to just the squish / quench areas or making the wall there thinner can allow a higher compression ratio with the same fuel.

Bottom line - without a deep knowledge and understanding of the 3D flow in the chamber it requires experimentation to find the optimum, but the experimentation requires an understanding of the above principles and more to be ultimately successful.

[Carnut1]

DV wrote about testing losing power when tightening quench in certain engines, possibly the Mini Cooper.

The Avenger, that design did not like quench.

[ptuomov]

It is clear that the two are part of the same but not exactly the same. Some general guidelines (sometimes conflicting):
1. Smaller clearance generally speeds up combustion by increasing turbulent intensity, if the combustion process was optimized, this can lead to a power loss.
2. A 1 degree taper usually leads to better results as a parallel clearance can lead to trapped end gas with piston rocking, leading to trapped end gas and more pre-ignition / detonation.
3. Directing the squished flow to the spark plug tip often leads to improvements but sometimes screws up the bulk flow in the chamber which leads to worse power.
4. Sometimes adding more waterflow to just the squish / quench areas or making the wall there thinner can allow a higher compression ratio with the same fuel.

Bottom line - without a deep knowledge and understanding of the 3D flow in the chamber it requires experimentation to find the optimum, but the experimentation requires an understanding of the above principles and more to be ultimately successful.

I think there are still some large eddy simulation research available on the web that is for port-injected four-valve engines. All the new research appears to be just gasoline direct injection.

In any case, it's my understanding that in a port-injected four-valve engine, the mixture motion is a tumble which rotates down from the exhaust side and up from the intake side. An efficient tumble is produced by valve angles such that the exhaust valve is normal to intake port angle. That is, the intake port flow (not valve, but flow from the port) uses the closed exhaust valve face as an efficient diffuser that has just the correct angle for a diffuser. This way, the tumble has a lot of energy and persists longer, close the the end of the compression stroke. During the compression stroke end, the tumble motion accelerates before breaking up into smaller motions, but based on my reading the charge still flows towards the exhaust side near the roof and towards the intake side near the piston dish during the combustion.

Here's an idea: How about angling the intake squish pad in the head by a couple of degrees and angling the exhaust squish pad in the piston by a couple of degrees. This way, by my logic, the squish pad angles reinforce the existing large tumble motion, and hopefully make combustion more consistent. Intake side squish pushes charge towards the spark plug on the top and exhaust squish pad pushes the charge towards the intake side on the bottom. Any merit to the idea?

[DrillDawg]

It's not going to be worth the trouble doing anything other than getting the clearance between .030 to .045" for a steel rod engine as long as you have enough squish area..

[Powertrip]

Many, many years ago I had a technical pamphlet that discussed modifying the Mopar Max Wedge engines, I don't remember the title or author.
What I do recall was that quench clearance was experimented with between .040" and .100", and that maximum power was found at .060".
The BBM has a large quench area percentage due to the valves being offset towards the sparkplug side of the combustion chamber ( NOT ideal for flow!! ), so that makes some sense to me.
That being said, I have not personally experimented with larger than the standard .040" quench clearance.

[ptuomov]

Many, many years ago I had a technical pamphlet that discussed modifying the Mopar Max Wedge engines, I don't remember the title or author.
What I do recall was that quench clearance was experimented with between .040" and .100", and that maximum power was found at .060".
The BBM has a large quench area percentage due to the valves being offset towards the sparkplug side of the combustion chamber ( NOT ideal for flow!! ), so that makes some sense to me.
That being said, I have not personally experimented with larger than the standard .040" quench clearance.

Was the compression ratio held constant?

[Powertrip]

Since this was over 40 years ago, I don't remember.
Since this pamphlet was about race engines only, I would assume they were maximizing compression ratio in each experiment.

[user-30257]

Very efficient heads and high compression (16-18:1) can be hard to tune, even in naturally aspirated trim. Using a softened chamber can help.

I have seen a few negative quench (guy read it in a book)

Zero deck bowtie block 11x heads .015 gasket. This roundy round engine made it 30 laps. Team owner brought it to me. He told me he wanted to build a quench engine because he read it would make more power and he could use less costly gas. He learned.

I see tight quench not that big of a deal with good heads and good piston designs. As far as the old stuff.. I don't remember as it's been too long ago since I used anything stock that is older than 25 years.

[dwilliams]

I have run it so tight that the .030 stamped on the piston imprints it self on to the head and never seen a ill effect on HP ..

Same here. I theoretically had .015" clearance between the piston and head, but rock and stretch let me see the piston size numbers mirrored in the quench part of the head.

I cut the pistons down to zero deck instead of +.015 and put it back together. It sounded soggy, throttle response was softer, and it felt like it lost 25hp. Yeeow.

I was a bit panicked when I saw signs of piston/head contact, but in retrospect, there was no shiny metal, just a thin area in the carbon layer. And the piston's velocity crosses zero as it passes TDC, so it's not like it's slamming into the quench area.

[hoffman900]

Stan and David has it right, but some more explanations:

There are two functions:
1. Cooling end gasses to stop detonation, from there the name Quench
2. Enhancing the turbulent intensity to speed up combustion by squeezing out the mixture, from there the name Squish

It is clear that the two are part of the same but not exactly the same. Some general guidelines (sometimes conflicting):
1. Smaller clearance generally speeds up combustion by increasing turbulent intensity, if the combustion process was optimized, this can lead to a power loss.
2. A 1 degree taper usually leads to better results as a parallel clearance can lead to trapped end gas with piston rocking, leading to trapped end gas and more pre-ignition / detonation.
3. Directing the squished flow to the spark plug tip often leads to improvements but sometimes screws up the bulk flow in the chamber which leads to worse power.
4. Sometimes adding more waterflow to just the squish / quench areas or making the wall there thinner can allow a higher compression ratio with the same fuel.

Bottom line - without a deep knowledge and understanding of the 3D flow in the chamber it requires experimentation to find the optimum, but the experimentation requires an understanding of the above principles and more to be ultimately successful.

Here is a great article Neels authored to go with the above: http://home.earthlink.net/~scloughn/id21.html

[groberts101]

Stan and David has it right, but some more explanations:

There are two functions:
1. Cooling end gasses to stop detonation, from there the name Quench
2. Enhancing the turbulent intensity to speed up combustion by squeezing out the mixture, from there the name Squish

It is clear that the two are part of the same but not exactly the same. Some general guidelines (sometimes conflicting):
1. Smaller clearance generally speeds up combustion by increasing turbulent intensity, if the combustion process was optimized, this can lead to a power loss.
2. A 1 degree taper usually leads to better results as a parallel clearance can lead to trapped end gas with piston rocking, leading to trapped end gas and more pre-ignition / detonation.
3. Directing the squished flow to the spark plug tip often leads to improvements but sometimes screws up the bulk flow in the chamber which leads to worse power.
4. Sometimes adding more waterflow to just the squish / quench areas or making the wall there thinner can allow a higher compression ratio with the same fuel.

Bottom line - without a deep knowledge and understanding of the 3D flow in the chamber it requires experimentation to find the optimum, but the experimentation requires an understanding of the above principles and more to be ultimately successful.

Here is a great article Neels authored to go with the above: http://home.earthlink.net/~scloughn/id21.html

You're right, that is a well summed up post. Takes me two pages to get even half those thoughts out there.